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  <div class="section" id="module-imghdr">
<h1>22.8. <tt class="xref docutils literal"><span class="pre">imghdr</span></tt> &#8212; Determine the type of an image<a class="headerlink" href="#module-imghdr" title="Permalink to this headline">¶</a></h1>
<p>The <tt class="xref docutils literal"><span class="pre">imghdr</span></tt> module determines the type of image contained in a file or
byte stream.</p>
<p>The <tt class="xref docutils literal"><span class="pre">imghdr</span></tt> module defines the following function:</p>
<dl class="function">
<dt id="imghdr.what">
<tt class="descclassname">imghdr.</tt><tt class="descname">what</tt><big>(</big><em>filename</em><span class="optional">[</span>, <em>h</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#imghdr.what" title="Permalink to this definition">¶</a></dt>
<dd>Tests the image data contained in the file named by <em>filename</em>, and returns a
string describing the image type.  If optional <em>h</em> is provided, the <em>filename</em>
is ignored and <em>h</em> is assumed to contain the byte stream to test.</dd></dl>

<p>The following image types are recognized, as listed below with the return value
from <a title="imghdr.what" class="reference internal" href="#imghdr.what"><tt class="xref docutils literal"><span class="pre">what()</span></tt></a>:</p>
<table border="1" class="docutils">
<colgroup>
<col width="26%" />
<col width="74%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Value</th>
<th class="head">Image format</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="docutils literal"><span class="pre">'rgb'</span></tt></td>
<td>SGI ImgLib Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'gif'</span></tt></td>
<td>GIF 87a and 89a Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'pbm'</span></tt></td>
<td>Portable Bitmap Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'pgm'</span></tt></td>
<td>Portable Graymap Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'ppm'</span></tt></td>
<td>Portable Pixmap Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'tiff'</span></tt></td>
<td>TIFF Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'rast'</span></tt></td>
<td>Sun Raster Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'xbm'</span></tt></td>
<td>X Bitmap Files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'jpeg'</span></tt></td>
<td>JPEG data in JFIF or Exif formats</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'bmp'</span></tt></td>
<td>BMP files</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">'png'</span></tt></td>
<td>Portable Network Graphics</td>
</tr>
</tbody>
</table>
<p>
<span class="versionmodified">New in version 2.5: </span>Exif detection.</p>
<p>You can extend the list of file types <tt class="xref docutils literal"><span class="pre">imghdr</span></tt> can recognize by appending
to this variable:</p>
<dl class="data">
<dt id="imghdr.tests">
<tt class="descclassname">imghdr.</tt><tt class="descname">tests</tt><a class="headerlink" href="#imghdr.tests" title="Permalink to this definition">¶</a></dt>
<dd><p>A list of functions performing the individual tests.  Each function takes two
arguments: the byte-stream and an open file-like object. When <a title="imghdr.what" class="reference internal" href="#imghdr.what"><tt class="xref docutils literal"><span class="pre">what()</span></tt></a> is
called with a byte-stream, the file-like object will be <tt class="xref docutils literal"><span class="pre">None</span></tt>.</p>
<p>The test function should return a string describing the image type if the test
succeeded, or <tt class="xref docutils literal"><span class="pre">None</span></tt> if it failed.</p>
</dd></dl>

<p>Example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">imghdr</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">imghdr</span><span class="o">.</span><span class="n">what</span><span class="p">(</span><span class="s">&#39;/tmp/bass.gif&#39;</span><span class="p">)</span>
<span class="go">&#39;gif&#39;</span>
</pre></div>
</div>
</div>


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